31x10.50s will fit with no lift on an r50.
as for other things you may want to get if your going to turn into a serious offroad enthusiast/weekend warrior would be skids...
which can be found here
Black Panther Skidplates
(I personally recommend these)
or here
Automotive Customizer Skidplates
pic of pathy on 31x10.50 bfg at's, no lift
pic of pathy on 265/75, no lift
Lift AND 32s (and 15x8 backspaced rims)
(thats dans aka vengeful)
LIFT and 31s
Lift and 31s on 15x8 backspaced rims
Hope that info helps.
As per brush guard, sometimes they can cause more damage than protection (NOT always the case) but since you have an 2002 you can fit an arb bull bar bumper, they come with a pretty heavy pricetag but people who have them will say they are well worth it.